A small form-factor pluggable (SFP) transceiver, which is also called an optical module, is a small form-factor pluggable optical transceiver, which is used for optical communication applications in telecommunications and data communications and is generally packaged in a standard SFP cage. A compact SFP (CSFP) is an optical module in which two single-fiber bidirectional optical transceivers are packaged in a standard SFP cage. A device for which a CSFP is used can have a doubled quantity of ports with a quantity of optical module cages remaining the same, which can meet requirements for high density and low costs.
Although a single-fiber bidirectional optical transceiver is used for a CSFP, two pairs of receive and transmit lines are still needed when an optical module cage in which the CSFP is packaged is connected to a socket of a communications device that supports an optical module. Therefore, a transmit signal of a second transceiver in the CSFP needs to occupy a pin of an availability signal of an optical module cage; in this case, whether the optical module is available cannot be determined by using a level of the availability signal.
A manner of using system software to perform I2C polling is generally used to determine whether an optical module is available in an SFP cage, that is, the system software sends a request signal to an Inter-Integrated Circuit (I2C or I2C) path corresponding to each optical module cage, and then determines, according to whether a response is received from the I2C path, whether an optical module is available. However, the I2C polling performed by the system software occupies a large quantity of central processing unit (CPU) resources, resulting in an increase of CPU usage. In addition, there is a polling period when the I2C polling is performed by using the system software. If there are a relatively large quantity of optical module cages, the polling time is long, and whether an optical module is available in an SFP cage cannot be monitored in real time. Further, because the I2C polling time is long, fast insertion and removal operations on the optical module may not be sensed when the I2C polling is performed by using the system software.